Fluid transportation by a sample

ABSTRACT

Apparatuses and methods are provided for transporting fluid to a sample such as a sheet of material. The apparatuses and methods may employ a variety of interfaces that facilitate controlled fluid transportation from a lumen for absorption by the sample.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/147,637, filed Jun. 27, 2008, entitled “Fluid Transportationby a Sheet of Material,” by Andrew Kallmes, now allowed, which claimspriority to U.S. Provisional Patent Application Ser. No. 60/946,707,filed Jun. 27, 2007, entitled “Fluid Transportation by a Sheet ofMaterial,” by Andrew Kallmes, the disclosures of which are incorporatedby reference in their entireties.

BACKGROUND

1. Field of the Invention

The invention relates generally to apparatuses and methods for measuringthe fluid transportation and/or absorption behavior of sheet materialsand other samples.

2. Description of Related Art

The desirability and performance characteristics of numerous sheetmaterials depend in large part on their fluid-transportation and/orabsorption behavior. For example, paper towels, tissues, and othercellulosic sheets are often evaluated by their ability to absorb waterand fluids containing liquid water. Similarly, numerous fabrics havebeen developed for their ability to absorb and wick moisture from asurface, e.g., wick perspiration from skin. Examples of such fabricsinclude a weft knits, denier gradient textiles and assorted laminatessuch as those described in U.S. Pat. No. 5,735,145 to Pernick and U.S.Pat. No. 5,0212,80 to Farnworth et al.

There are presently several methods and apparatus for determining thefluid-transportation properties of materials. For example, U.S. Pat. No.5,138,870 to Lyssy describes an apparatus for measuring the water vaporpermeability of sheet materials under adjustable constant measuringconditions. A lid having an air inlet opening and an outlet opening isattached on a cup containing water in a vapor and airtight manner. Asheet material having its circumferential border held between the rimsof the cup and lid separates the water in the cup from the lid. Anabsorption member containing a moisture-absorbent material is incommunication with the outlet opening. A blower in communication withthe air inlet opening aspirates air through an air dryer and blows theresulting dry air into the sealed cup containing the sheet material. Asa result, the permeability of the sheet material may be measured.

For liquid absorption testing, U.S. Pat. No. 4,357,827 to McConnell(hereinafter the “827 patent”) describes a gravimetric absorbency testerthat determines the wicking properties of a material by determining theweight of liquid flowing to or from a test site. The apparatus includesa vessel for containing liquid supported solely by a balance, anindicator for indicating the weight sensed by the balance, a testsurface containing the test site on which a specimen to be tested mayreceived, a conduit operatively connecting the vessel to the test sitefor directing a flow of liquid between the vessel and test site, and anadjuster for vertically positioning the test site. The surface of theliquid in the vessel is maintained at a constant elevation as liquidflows into and out of the vessel.

One problematic issue associated with generally all liquid absorptiontesting involves the interface through which liquid is introduced intothe specimen. For example, when the technology described the '827 patentis used, the test specimen is placed on a test plate having a holethough which liquid may be directed in an upward direction toward thespecimen. This is problematic because fluid may preferentially wickalong in the boundary between the specimen and the test plate instead ofbeing absorbed the test specimen. In some instances, the test plate maybe preferentially wetted over the specimen. Any fluid not absorbed bythe specimen may represent a source of testing error.

In addition, a means may be required to provide sufficient activationenergy to induce the liquid from the hole to wet the specimen and toliquid absorption by the specimen. Such means may, for example, includea pinch valve that allows liquid to be forced through the hole at avelocity that allows the liquid to contact the specimen and overcomesurface forces against wetting. Such means may compromise tests designedto measure the intrinsic absorption properties of the test specimenbecause they introduce excess measurement noise.

Previously known technologies also have generally failed to addresscertain problems associated with the delivery of liquid to the specimen.For example, the technology described in the '827 patent employs aconduit operatively connecting the vessel to the test site for directinga flow of liquid between the vessel and test site. As shown in FIG. 1 ofthe '827 patent, the conduit defines a flow path that travels through anelevated local peak plateau region above both the vessel and the testsite before reaching the test site. Such a flow path also tends tocompromise tests designed to measure the intrinsic absorption propertiesof the test specimen because they introduce measurement errorsassociated with uneven or uncontrolled liquid flow. Such errors mayarise, for example, due to the tendency of the conduit to trap air orother gasses.

Still another problematic issue associated liquid absorption testing isthat test specimens may swell and/or deform as they absorb liquid. As aresult, the test specimens in part or in whole may be displaced relativeto the surface from which test specimens absorb liquid during testing.In turn, liquid transport behavior may be disrupted or otherwisealtered, thereby compromising the accuracy of the test.

Accordingly, there exist opportunities to provide alternatives andimprovements to known methods and apparatuses for determining thefluid-transportation properties of materials, particularly for thepurpose of overcoming any shortcomings associated with known methods andapparatuses.

SUMMARY OF THE INVENTION

Apparatuses and methods are provided for transporting fluid to a sheetof material. Typically, the sheet is immobilized on an upper surface ofa support structure. The upper surface of the support structure may bebounded by a periphery and may contact a minority portion, e.g., no morethan 10% of a lower surface, of the sheet within the periphery. Acontainer holding a fluid is provided along with a conduit having afluid-conveying lumen that extends from the container to one opening orbranches from the container into a plurality of terminal openings facingthe lower surface of the sheet. Optionally, a porous medium is placed influid communication with the fluid-conveying lumen and in contact withthe lower surface of the sheet. The medium has wetting propertieseffective to allow the fluid to be wicked from the lumen against gravityvia capillary action. Once transported to an upper surface of the porousmedium, the sheet absorbs the fluid from the medium. By measuring thefluid transported from the container, fluid-transport and/or absorptionproperties of the sheet may be assessed.

In another embodiment, an assembly for wetting a sheet of material isprovided. The assembly includes a sheet of material supported by asupport structure as described above. A means for immobilizing the sheeton support structure, e.g., a weight having substantially coplanar lowerexterior and interior surfaces, may be placed in contact with the uppersurface of the sheet.

In still another embodiment, the invention provides a method forassessing fluid-transportation anisotropy by a sheet of material havingan upper surface and a lower surface. The method involves obtaining datafrom a first absorption test that employs a single wetting interface ata lower surface of a first test sheet of the material and obtaining datafrom a second absorption test that employs a plurality of wettinginterfaces at a lower surface of a second test sheet of material. Thedata for the first and second absorption tests are compared to determineany differences between radial and axial fluid-transporting behavior thesheet of the material over time, optionally relative to saturation.

In a further embodiment, an apparatus is provided for transporting fluidto a sheet of material as generally described above but with a means forpositioning an interfacing portion of the sheet to absorb fluid throughthe opening. Such positioning means may include, for example, a memberfor controllably pressing the interfacing portion of the sheet throughthe opening. The member may include a screw that has spiral grooves thatallows for controllable positioning of the member relative to the weighton the sheet.

In a still further embodiment, a method is provided wherein a sheet isin a horizontal orientation on upper surface of a support. Fluid isdirected from a container through a fluid-conveying lumen of a conduitthat extends from the container to a terminal opening facing the lowersurface of the sheet such that a negative head is defined between thelower surface of the sheet and the fluid in the opening. An interfacingportion of the sheet is lowered to absorb fluid through the openingagainst gravity.

In yet another embodiment, an apparatus transports a fluid to a sample.The apparatus includes a support structure supporting the sample, acontainer holding the fluid. A that has a fluid-conveying lumen definesa fluid flow path extending from a first terminal opening at thecontainer to a second terminal opening below the sample. Optionally, theflow path may not exhibit an elevated local peak region between thefirst and second terminal openings. A means is provided for facilitatingthe sample to absorb the fluid from the second terminal opening. Thefacilitating means may include, for example, a porous medium, or a meansfor positioning an interfacing portion of the sample to absorb fluidthrough the second terminal opening against gravity. The facilitatingmeans may exclude a pinch valve.

In a yet further embodiment, the invention provides a support structurefor supporting a sample having a lower surface in a horizontalorientation. The structure includes a plurality of support members, afixture for immobilizing the support members relative to each other, anda means for immobilizing a conduit having a fluid-conveying lumenrelative to the support members. The support members have coplanar uppersurfaces that define a wetting plane on which the lower surface of thesample may be placed. At least a portion of the lumen may extend upwardtoward an interface near or within the wetting plane to transport fluidalong a flow path that terminates at the lower surface of the sample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B, collectively referred to as FIG. 1, depict simplifiedembodiments of the invention in the form of apparatuses that use aporous medium for wicking fluid upward via capillary action to evaluatefluid transportation properties of a sheet of material in a horizontalorientation. FIG. 1A shows in schematic cross-sectional exploded view anembodiment wherein a conduit is connected to an outlet port extendingthrough a submerged portion of a container of liquid. FIG. 1B shows inschematic cross-sectional exploded view an embodiment wherein theconduit is arranged in manner that requires a siphoning action totransport liquid over the top of the container.

FIGS. 2A, 2B, and 2C, collectively referred to as FIG. 2, depict a webplate and a porous sheet of material suitable for use as the sampleholder of the invention. FIG. 2A shows the web plate in simplifiedschematic top view. FIG. 2B shows a simplified schematic cross-sectionalview of the web plate along a plane indicated by dotted line A with aporous sheet on an upper surface thereof FIG. 2C is a photograph of anexemplary web plate having a sheet on an upper surface thereof held nextto an optional weight. FIG. 2D is a photograph of the same web plate andsheet with the weight held over the sheet.

FIGS. 3A, 3B, and 3C, collectively referred to as FIG. 3, depict a priorart support plate that contacts greater than a majority of a lower sheetsurface. FIG. 3A schematically shows in top view the support platewithout a sheet on an upper surface thereof. FIG. 3B shows incross-sectional schematic view the support plate along a plane indicatedby dotted line B with a sheet on an upper surface thereof FIG. 3C is aphotograph of a prior art support plate.

FIGS. 4A, 4B, 4C, and 4D, collectively referred to as FIG. 4, depict aweight suitable for use with the invention. FIG. 4A schematically showsthe weight in top view. FIG. 4B schematically shows the weight in bottomview. FIG. 4C schematically shows the weight in cross sectional viewalong a plane indicated by dotted line C. FIG. 4D is a photograph or anexemplary weight similar to that depicted in FIGS. 4A-4C.

FIG. 5 schematically depicts a simplified embodiment of the invention inthe form of an apparatus similar to that shown in FIG. 1A except aplurality of porous media is provided, each in communication with adifferent terminal opening.

FIGS. 6A, 6B, 6C, and 6D, collectively referred to as FIG. 6, depict anembodiment of the invention in the form of an apparatus that use acenter screw to position an interfacing portion of a sheet in acontrollable manner to evaluate fluid transportation properties of asheet of material. FIG. 6A shows in schematic cross-sectional view theembodiment that exhibits a negative head arrangement that prevents thesheet from absorbing fluid through a terminal opening of the conduit.FIG. 6B shows in schematic cross-sectional view the embodiment whereinthe center screw is used to depress the interfacing portion of the sheetinto the conduit to absorbing fluid through the terminal opening. FIG.6C is a photograph of the weight, shown in FIGS. 6A and 6B, the weighthaving a center screw in a generally raised position relative to theweight's body. FIG. 6D is a photograph of the weight shown in FIG. 6C,wherein the center screw is set in a lowered position such that itslower surface extends past the lower surface of the weight's body.

FIGS. 7A, 7B, 7C, and 7D, collectively referred to as FIG. 7, depict anexemplary support structure of the invention that includes a plate witheight fins. FIG. 7A shows the support structure in simplified schematictop view. FIG. 7B shows a simplified schematic cross-sectional view ofthe support structure along a plane indicated by dotted line D with aporous sheet sample on an upper surface thereof. FIG. 7C is a photographof a support structure similar to that depicted in FIGS. 7A and 7Bexcept with fourteen fins in a right-side-up orientation supported by aplastic cup. FIG. 7D is a photograph of the support structure shown inFIG. 7C except in an upside-down orientation.

DETAILED DESCRIPTION OF THE INVENTION

Before describing the present invention in detail, it is to beunderstood that the invention is not limited to specific fluids orporous media, as such may vary. It is also to be understood that theterminology used herein is for describing particular embodiments only,and is not intended to be limiting.

In addition, as used in this specification and the appended claims, thesingular article forms “a,” “an,” and “the” include both singular andplural referents unless the context clearly dictates otherwise. Thus,for example, reference to “an opening” includes an arrangement ofopenings as well as a single opening, reference to “fluid” includes asingle fluid as well as a mixture of fluids, and the like.

In this specification and in the claims that follow, reference will bemade to a number of terms that shall be defined to have the followingmeanings, unless the context in which they are employed clearlyindicates otherwise:

The term “array” is used herein in its ordinary sense and refers to anordered arrangement of features, e.g., holes, in one, two, or threedimensions, e.g., rectilinear grids, parallel stripes, spirals, and thelike.

The terms “cellulose, “cellulosic” and the like are used herein in theirordinary sense and refer to a complex carbohydrate or polysaccharidethat includes a plurality of monomeric glucose units (C₆H₁₀O₅). As iswell known in the art, cellulose constitutes the chief part of the cellwalls of plants, occurs naturally in fibrous products such as cotton andlinen, and is the raw material of many manufactured goods such as paper,rayon, and cellophane.

The term “fluid” is used herein in its ordinary sense and refers tomatter that is nonsolid or at least partially gaseous and/or liquid. Afluid may contain a solid that is minimally, partially or fullysolvated, dispersed or suspended. Examples of fluids include, withoutlimitation, aqueous liquids (including water per se and salt water) andnonaqueous liquids such as organic solvents and the like.

The term “head” refers to the relative positions between a fluid sourceand a support on which an interfacing portion of a sheet may be placedto absorb fluid from the source. A “negative head” refers to anarrangement in which the sheet does not absorb fluid without from thesource in the absence of added activation energy to initiate absorption.

The term “substantially identical” as used to describe a plurality ofitems indicates that the items are identical to a considerable degree,but that absolute identicalness is not required. For example, whenopenings are described herein as of a “substantially identical size,”the openings' size may be identical or sufficiently near identical suchthat any differences in their size are trivial in nature and do notadversely affect the performance of the openings' function. The terms“substantial” and “substantially” are used analogously in other contextsinvolve an analogous definition.

In general, the invention relates to apparatuses for measuring wettingand/or other mechanisms of fluid transportation by a sheet of materialor some other sample. Typically, the sheet or sample has upper and lowersurfaces and is immobilized on an upper surface of a support structure.A container holding a fluid is provided with a conduit having afluid-conveying lumen that extends from the container to a terminalopening facing the lower surface of the sheet or sample. The sheet orsample is positioned to absorb fluid from the terminal opening. A meansmay be provided for measuring and/or monitor the amount of fluid in thecontainer to determine the fluid-transportation or absorption propertiesof the sheet.

Typically, the invention is practiced in a manner that provides anaccurate means for determining the intrinsic fluid-transportingproperties and behavior of the sheet. In contrast to prior arttechnologies, the invention minimizes systemic measurement error, e.g.,those that may arise through the inappropriately forceful introductionof fluid into the sheet. That is, the invention provides a facilitatingmeans to deliver fluid for absorption by a sheet at a rate that matchesthe intrinsic transporting rate of the sheet. In some embodiments, a“controlled puddle” is provided from which a sheet interfaced therewithmay absorb fluid in a manner such that fluid-transport dynamics areoverwhelming dominated by the intrinsic properties of the sheet ratherthan by the manner in which fluid is initially delivered to the sheet.In other embodiments, a means is provided to ensure that only aninterfacing portion of the sheet is controllably lowered and maintainedin position to absorb fluid from the terminal opening.

The invention may be practiced to ensure the intrinsic properties of thesheet dominate the dynamics of fluid-transportation. For example, theinventive apparatus may be constructed such that the upper surface ofthe support structure is bounded a periphery and contacts a minorityportion (e.g., no more than about 5% to about 10%) of the lower surfaceof the sheet within the periphery, so that only a minority portion forthe sheet's lower surface is subject to interfacial fluid-transportationeffects. Optionally, a porous medium is placed in fluid communicationwith the fluid-conveying lumen and in contact with the lower surface ofthe sheet. The medium may have wetting properties effective to allow themedium to wick fluid from the lumen against gravity via capillary actionand to allow the sheet to absorb the fluid from the medium.

As another example, the support structure may include a plurality ofsupport members, a fixture for immobilizing the support members relativeto each other, and a means for immobilizing a conduit relative to thesupport members. The support members may have coplanar upper surfacesthat define a wetting plane on which the lower surface of the sample maybe placed. At least a portion of a lumen within the conduit may extendupward toward an interface near or within the wetting plane to transportfluid along a flow path that terminates at the lower surface of thesample. The support members may be arranged to minimize signal noiseassociated with the dynamics of fluid transportation between the uppersurfaces of the support members and the lower surface of the samplerelative to the intrinsic absorption properties of the sample.

A simplified exemplary embodiment of the inventive apparatus isschematically depicted in FIG. 1. As with all figures referenced herein,in which like parts are referenced by like numerals, FIG. 1 is notnecessarily to scale, and certain dimensions may be exaggerated forclarity of presentation. Referring to FIG. 1, the apparatus 10 includesa container 12, which acts as a reservoir that holds or serves as asource of a liquid 14 to be employed in testing the performance of asuitable sample sheet 30 of material. As shown, the container 12 has anupper opening 16 through which liquid 14 may be added.

Also shown is a conduit 20 having a fluid-conveying lumen 22 thatextends from a first terminal opening 23 at or near a submerged portionof the container 12 to a second terminal opening 24, thereby defining aflow path for the fluid, e.g., liquid 13, to be transported from thecontainer 12 to the second terminal opening 24. The conduit maytransport liquid from the container in various ways. In FIG. 1A, forexample, the first terminal opening 23 of the conduit is connect to aport 17 extending through a container wall 18 and located at a submergedportion of the container 12. Thus, the flow path shown in FIG. 1A doesnot exhibit an elevated local peak region. The absence of an elevatedlocal peak region tends promote fluid flow at a rate controlled by theintrinsic absorption properties of the sample 30 rather than by thephysical characteristics or geometry of the flow path. Notably, no pinchvalve is placed within the flow path.

In contrast, as shown in FIG. 1B, the conduit 20 may extend in aconfiguration that allows liquid 14 to be siphoned from a first terminalopening 23 through the flow path that extends upwardly through upperopening 16 of the container 12 and over the top of container wall 18toward the second terminal opening 24. Thus, in contrast to FIG. 1A, theflow path in FIG. 1B exhibits an elevated local peak region 19 locatedat a height above both the container and the sample. If such a flow pathis used, liquid 14 is preferably siphoned for the apparatus shown inFIG. 1B in a manner that does not trap any air or other gas pockets inthe conduit lumen 22. Optionally, a pinch valve (not shown) may beplaced within the flow path to provide additional wetting activationenergy.

It should be noted that different liquids may have different propertiesthat may dictate the geometry and construction of the conduit and flowpath between wetting properties and the container and the sample. Forexample, water is a polar liquid whereas oils in general are considerednonpolar. Water and oils exhibit different cohesive, adhesive, andsurface tension properties. It has been found that certain liquids,e.g., water, perform well in flow paths that require initial siphoning,but that other liquids, e.g., oils, do not. Thus, for oils, flow pathshaving elevated local peak regions should be avoided.

The sheet 30 has an upper surface 32 and a lower surface 34 and isinterposed in a horizontal orientation between a support structure 40and a means for immobilizing the sheet in the form of a weight 50 placedon the upper surface 32 of the sheet 30. As shown, the weight 50 mayhave a lower interior surface 52 and a lower exterior surface 54 thatcontacts the upper surface 32. The support structure 40 has an uppersurface 42 bounded by a periphery 44. As discussed in detail below, thesupport structure 40 may include a web plate having an upper surface 42that contacts no more than 10% of the lower sheet surface 34 within theperiphery 44.

The second terminal opening 24 of the lumen 22 is positioned in facingrelationship to the lower surface 34 of the sheet 30. Typically, theopening 24 is positioned at a height such that it lies in horizontalplane “L,” as generally defined by the meniscus surface 15 of the liquid14 in the reservoir vessel 12. Typically, the horizontal plane L is awetting plane. Care must be taken in positioning opening 24 relative toplane L. If the opening 24 is elevated relative to plane L, a means maybe required to provide sufficient activation energy to induce the liquidfrom the hole to wet the sheet 30. However, if the opening 24 is locatedbelow plane L, liquid will tend to flow out of opening 24.

A facilitating means in the form of a porous medium 60 is placed influid communication with the lumen 22. As a result, the medium 60extends from terminal opening 24, and an upper surface 62 of the medium60 contacts the lower surface 34 of the sheet 30. Notably, the medium 60contacts a portion of the sheet 30 generally bounded by lower interiorsurface 52 of the weight. The medium 60 has wetting properties effectiveto allow liquid 14 to be wicked upward via capillary action toward thesheet 30.

In operation, the sheet 30 to be tested is placed on the top surface 42of the support structure. The weight 50 is placed on the sheet 30 sothat both lower surfaces 52 and 54 contacts the upper sheet surface 32.As the terminal opening 24 is positioned in substantially the same levelas the surface 15 of the liquid 14 in the container 12, liquid 14 isfree to flow from the container 12 to terminal opening 24 due togravitational forces when valve 28 in the conduit 20 is opened. Theporous medium 60 wicks liquid 14 from the opening 24 of the lumen 20against gravity via capillary action toward surface 62, therebyeffectively providing a controlled puddle.

Then, sheet 30 then absorbs liquid 14 from the container 12. Typically,the container 12 holds a sufficiently large volume of liquid such thatthe level of the surface 15 does not substantially change while liquid14 is absorbed by the sheet 30. That is, the porous medium 60 may serveas a “controlled puddle” interface to an effectively limitless amount ofliquid for absorption by the sheet 30. If, however, a smaller amount ofliquid is used, a mechanism may be used to maintain relative height ofthe opening 24 and the liquid surface 15 in the container 12.

By monitoring the quantity of liquid in the container 12 before anyliquid 14 has flowed from the container 12 to the sheet 30, and theweight after all absorption by the sheet 30 has ceased, the total amountof liquid taken up by the test sheet 30 may then be determined. Theapparatus can also be employed to evaluate the absorbency rate of aspecimen by noting the volumetric or weight change of liquid in thecontainer over a period of time.

In other words, a method is provided for transporting fluid forabsorption by a sheet of material having an upper surface and a lowersurface. The sheet is placed in a horizontal orientation on uppersurface of a support such that the upper surface of the supportstructure contacts no more than 10% of the lower surface of the sheetwithin a periphery bounding the upper surface. Fluid is directed from acontainer through a fluid-conveying lumen of a conduit that extends fromthe container to a terminal opening facing the lower surface of thesheet. A porous medium in fluid communication with the fluid-conveyinglumen and in contact with the lower surface of the sheet is allowed towick fluid from the lumen against gravity via capillary action and toallow the sheet to absorb the fluid from the medium. Optionally, thefluid in the container is measured repeatedly while the fluid flowsthrough the lumen and/or the porous medium.

FIG. 2 shows in detail the web plate 40 suitable for use with theinvention. As shown in FIG. 2A, the web plate includes a central websection 46 formed from a plurality of regularly-spaced intersectingfilaments 47 defining an array of through opening 48 of substantiallyidentical size and shape. As shown in FIG. 2B, the filaments 47 may bestretched under tension, be bounded by periphery 44, and define asubstantially planar upper horizontal surface. Optionally, filaments areinterlaced. When a sheet 30 is placed on the upper surface 42 of the webplate 40, only a small portion, e.g., less than 5% to 10%, of the lowersheet surface 34 contacts the web section 46, since the web section 46area may include a greater portion of openings 48 than filaments 47. Asa result, only a small amount of fluid may collect about the boundarybetween the web plate 40 and the sheet.

In contrast, FIG. 3 shows a prior art support plate 40 that includes acentral opening 48 through which liquid may be introduced to the uppersupport plate surface 42. When a sheet 30 is placed on the upper supportplate surface 42, substantially then entirety of the lower sheet surface34 faces the upper support plate surface 42. As a result, fluid may poolor preferentially wet the boundary between the lower sheet surface 34and the upper support plate surface 42. As boundary fluid does notrepresent fluid transported solely as a result of the intrinsicabsorption properties of the sheet, sheet absorption measurements may becompromised.

Alternative support structures may be used as well. For example, asshown in FIG. 7, depicts a support structure 40 in the form of a finplate that may be used to replace the support structure shown in FIG. 1.The support structure 40 includes a plurality of support members 41 inthe form of fins. The fins 41 are immobilized relative to each other viaa fixture 43 in the form of a generally circular plate. The plate 43 hasan upper surface 43U, a lower surface 43L that is parallel to the uppersurface 43U, and a center through-hole 43H. The fins 41 extend upwardfrom upper plate surface 43U, terminate at rectangular, upper-finsurfaces 42, and are evenly spaced in a fan-out manner about the centerthrough-hole. The upper fin surfaces 42 surfaces are generally coplanarrelative to each other, parallel to the upper plate surface 43U, anddefine a wetting plane “L.”

Also included is interfacing component 43I. As shown, the interfacingcomponent extends through and is immobilized within the centerthrough-hole 43H of the plate 43. The interface includes an upperinterfacing opening 43IU and a lower interfacing opening 43IL. As shown,the upper interfacing opening 43IU may be located slightly below thewetting plane 42. The lower interfacing opening 43IL may be connected toand serve to immobilize a conduit 20 having a fluid-conveying lumen 22relative to the support members 41. As shown, the portion of the lumen22 may extend upward toward an interface near or within the wettingplane to transport fluid along a flow path that terminates at the lowersurface of the sample.

Fin plates of the invention may vary. For example, the fin plate shownin FIGS. 7C and 7D includes fourteen fins instead of the eight shown inFIGS. 7A and 7B. In addition, different materials may be used. Forexample, the fin plate shown in FIGS. 7C and 7D includes an opticallytransparent polymeric plate, a plurality of metallic fins, and anoptically opaque polymeric interface.

Support members may take forms other than that shown in FIG. 7. Forexample, support members may be provided as rectilinear arrays ofcolumnar or other geometries. In addition, the support members do nothave to be identical in size or shape.

In operation, the lower surface 34 of the sample 30 to be tested isplaced in contact with the top surface 42 of the support structure.Liquid 14 is free to flow through a flow path that extends through lumen22 upward and through interfacing component 43I located within thecenter through-hole 43H of the plate 43. Any of a number of facilitatingmean may be used to allow the sample to absorb liquid from the upperopening 43IU of the interfacing component.

It should be noted that certain samples may change shape as they absorbliquid. In such cases, the support structure should be chosen to accountfor such shape changes. For example, the support members should bechosen and arranged in a manner that deters the sample from saggingbetween the support members. It has been experimentally determined thatthe support structure depicted in FIG. 7 with fins arranged in aradially fan-out manner tends to reduce unwanted sample sagging betweensupport members relative to certain other support structures duringtesting, particularly for samples of single-ply toilet paper.

FIG. 4 depicts a weight 50 that may be used as means for immobilizingthe sheet on the upper support structure surface 42. As shown, theweight 50 may be comprised of a unitary piece having an upper surface51, and coplanar lower interior and exterior surfaces 52 and 54. Athrough hole 55 extends along vertical axis V through the weight andprovides communication between the upper surface 51 and the lowerinterior surface 52. The lower surfaces are substantially concentricabout axis V, which perpendicular to the plane of the lower surfaces.

When placed in operation, as shown in FIG. 1, the weight 50 is placed onthe upper sheet surface 32. The lower weight surfaces 52 and 54 serve tomaintain the substantial planarity of the sheet as the sheet is wet.Accordingly, the weight, like the support, may comprise or be coatedwith a hydrophobic material, e.g., silicones, fluorinated andperfluorinated polymers, polyolefins, certain acrylics, etc., at and/ornear the lower interior surface of the weight. In any case, the throughhole 55 allows an operator of the invention to view the initial wettingof the sheet 30.

Thus, in another embodiment, an assembly for wetting a sheet of materialis provided. That includes a sheet of material supported by a supportstructure as described above. A weight having substantially coplanarlower exterior and interior surfaces is placed in contact with the uppersurface of the sheet.

The invention may be used with any of a number of fluids. Typically, theinvention is used in combination with liquids, but fluids such asemulsions, suspension, etc. may also be compatible with the invention.In particular, the invention finds widespread use in combination withaqueous fluids, e.g., water-based saline solutions, though nonaqueousand/or organic fluids may be suitable for use with the invention.

The porous medium may vary as well. Typically, the porous medium issubstantially incompressible and may comprise a glass frit material.However, the porous medium may be compressible in some situations. Forexample, the porous medium may additionally or alternatively comprise asponge or other porous disposable material suitable for wicking fluidtoward the sample. Disposable materials are well suited for samples thatinclude fluid soluble components that may flow into the porous medium.

Depending on the requirements of the practitioner of the invention, theporous medium may be effective to transport the fluid from the lumen toa distance of at least about 3 to 5 millimeters upward against gravityvia capillary action. In addition, the overall construction of themedium may vary as well. For example, the porous medium may have asurface facing the sheet with an area of at least about 1 cm² or about 2cm² to about 4 cm². An exemplary medium for use with the invention mayhave a porosity of at least about 30% and a pore size and surfaceproperties appropriate for wicking the test fluid.

Any number of means may be used for measuring fluid in the container.For example, the fluid may be measured by weight. In some instances, thecontainer may be supported solely by a weight-sensing surface of aweighing means such as an electronic balance having a tare switch and adisplay. If desired, a force transducer or similar device may be usedinstead of a balance. In addition or in the alternative, optical and/orelectronic means may be used to measure the volume of the fluid in thecontainer. Additional fluid measuring means may include flow meters andother devices effective to measure and/or monitor a change in the fluidcontent in the container over a desired time period.

The invention may be used with any of a number of sheet materials. Forexample, the sheet may be at least cellulosic in part, e.g., a paperproduct. In addition or in the alternative, the sheet may comprise oneor more synthetic polymeric materials such as polyesters, polyamides,polyurethanes, polyethylene glycols, acrylic polymers, combinationsthereof, and copolymers of any of the foregoing. In some instances,sheets such as woven, laminate, and/or denier gradient fabrics may beused. Such so-called “high-performance wicking” fabrics may be used withor without chemical treatment in apparel that allows moisture to betransported away from a wearer, thereby balancing body temperature andenhancing comfort.

To measure the performance of such “high-performance wicking fabrics,”it is often necessary to approximate such fabrics in use, e.g., asexercise apparel. Since exercise apparel are often used in varyingoperating conditions, the invention may include additional features tosimulate these operating conditions. For example, a means may beprovided for increasing vapor transport at the upper surface of thesheet. Such vapor-transport-increasing means may includes a blowerand/or a suction device, e.g., to approximate wind conditions a runnermight experience. Similarly, a means may be for transporting fluidthrough the conduit at a predetermined rate, e.g., selected toapproximate human perspiration. Such means may include a pump, suctiondevice, and/or other fluid-transporting devices known in the art.

When the inventive apparatus includes a conduit having a fluid-conveyinglumen that extends from the container to plurality of terminal openingsfacing the lower surface of the sheet, the porous material may sometimesbe omitted. The terminal openings may form an array, e.g., a circulararray. The openings are may vary or be substantially identical in sizeand/or shape. When each opening has a circular shape, their diametersmay range from about 0.5 to about 6 mm, or more specifically, from about2 to about 4 mm.

In still another embodiment, the invention provides a method forassessing fluid-transportation anisotropy by a sheet of material havingan upper surface and a lower surface. The method involves obtaining datafrom a first absorption test that employs a single wetting interface ata lower surface of a first test sheet of the material and obtaining datafrom a second absorption test that employs a plurality of wettinginterfaces at a lower surface of a second test sheet of material. Thedata for the first and second absorption tests are compared to determineany differences between radial and axial fluid-transporting behavior thesheet of the material over time.

For example, a first absorption test may be carried out using anapparatus that includes a first test sheet and single wetting interfaceas shown in FIG. 1A. A second absorption test may be carried out using asecond test sheet substantially identical to the first test sheet and aplurality of wetting interfaces as shown in FIG. 5. If all wettinginterfaces are substantially identical, the initial uptake rate of thesecond test sheet should be proportional to the initial uptake rate ofthe first test sheet by the number of wetting interfaces used in thesecond test.

However, it should be also be apparent that the second sheet should besaturated more quickly than the first sheet. In addition, wetting of thefirst sheet is accomplished through a more horizontal (radial)absorption mechanism, while a more vertical (axial) absorption mechanismcontrols the wetting of the second sheet. Thus, by comparing the data ofthe two tests, those of ordinary skill in the art should be able toassess any differences between directional absorption properties of thesheets.

FIG. 6 depicts another simplified embodiment of the inventive apparatushaving some similarity to that shown in FIG. 1A. For example, theapparatus of FIG. 6 include a container 12 and a conduit 20 having afluid-conveying lumen 22 that extends from a first terminal opening 23to a second terminal opening 24 that faces support structure 40. Likethe conduit shown in FIG. 1A, the conduit 20 of FIG. 6 serves totransport liquid 14 from the container 12 test sample sheet 30, which isinterposed in a horizontal orientation between a support structure 40and weight 50. However, the apparatus of FIG. 6 does not include aporous medium between the conduit and the sample.

The weight 50 of FIG. 6 is also similar to that shown in FIG. 4 exceptthat it includes a guide 57 spanning across hole 55 that engages asingle screw 58 centered therein. The screw 58 may be lowered or raisedrelative to the guide 57 and other parts of the weight 50 by turning thescrew clockwise or counterclockwise, respectively. As a result, themovable screw 58 may serve as a means for positioning or maintaining theposition of an interfacing portion 35 of the sheet to absorb fluidthrough opening 24.

FIG. 6 shows that terminal opening 24 of the lumen 22 is positioned infacing relationship to the lower surface 34 of the sheet 30 at a heightslightly above horizontal plane “L” which is defined by surface 15A ofthe liquid 14 in the reservoir vessel 12. Accordingly, at equilibrium,liquid 14 forms a surface 15B that lies slightly below opening 24. Thatis, meniscus surfaces 15A and 15B both generally lie in plane L.

In operation, as shown in FIG. 6A, a sheet 30 to be tested is placed onthe support structure 40. The weight 50 is placed on the upper surface32 of sheet 30. As a result, the sheet is rendered substantiallyimmobile on the support structure.

As shown in FIG. 6A, sheet 30 does not contact meniscus surface 15B.That is, FIG. 6A depicts a negative head arrangement. Typical negativehead arrangements may be such that the opening or liquid meniscus islocated at least about one to about ten millimeters below the supportstructure and/or the sheet.

In general, when prior art negative-head liquid-absorption sheet testingequipment is used, testing may require one or both of two approaches toinitial liquid absorption. The first approach is to force or squirtliquid upward into the sample sheet on a support using a pinch valve orthe like. The second approach is to lower the support directly into theliquid to be absorbed. Both approaches tend to produce excessivemomentum-related artifacts that skew test data.

In contrast, as shown in FIG. 6B, the invention may involve the use ofthe center screw to deform the sample sheet 30 or manipulate only aportion of the sample sheet on the support structure 40 to initiateabsorption. As shown in FIG. 6B, the center screw 58 is slowly turned sothat is it presses gently downward against the 32 upper surface of thesheet's interfacing portion 35. As a result, at least the lower surface34 of the sheet's interfacing portion 35 travels through opening 24.When the sheet's interfacing portion 35 breaks meniscus 15B andeffectively becomes submerged in liquid 14 in lumen 12, sufficientactivation energy has been provided to allow the sheet 30 to beginabsorbing liquid. In effect, the screw 58 serves as a means to ensurethe establishment and maintenance of a single point interface betweenthe sample sheet and the liquid. Those of ordinary skill in the art willrecognize that the invention allows for a greater initial negative headthan known absorption testing technologies.

It should be noted that the construction of the weight shown in FIG. 6Bmay Fin plates of the invention may vary. For example, differentmaterials may be used. For example, as shown in FIGS. 6C and 6D, thebody of the weight may be formed from an optically transparent polymericmaterial, and the center screw may be formed from a metallic material.However, other combination of materials may be used as well.

Thus, the invention provides a number of advantages over knownabsorption testing equipment and methods. In general, the inventionprovides an improved interface through which liquid may be introducedinto the specimen for the duration of absorption testing. The improvedinterface may serve to: (1) reduce the activation energy required forinitiating absorption testing; (2) maintain contact between the liquidto be absorbed with the sheet or sample to be tested; (3) allow for agreater negative head; and (4) improve the repeatability of results byreducing the noise to signal ratio for the test results.

Variations of the present invention will be apparent to those ofordinary skill in the art in view of the disclosure contained herein andmay be discovered upon routine experimentation. For example, while acenter screw has been disclosed herein as a means for positioning aninterfacing portion of the sheet to absorb fluid through the openingagainst gravity member, other means may be used as well. In someinstances, the means may include levers, gears, pulleys, etc., inaddition to or instead of spiral grooves to allow controllablepositioning of the sheet's interfacing structure. Similarly, variousvertical leveling mechanisms known in the art may be used in conjunctionwith the support structure. Furthermore, while the above description hasfocused on samples in the form of an absorbent sheet, the invention maybe employed with samples of other forms as well.

It is to be understood that, while the invention has been described inconjunction with the preferred specific embodiments thereof, theforegoing description merely illustrates and does not limit the scope ofthe invention. Numerous alternatives and equivalents exist which do notdepart from the invention set forth above. For example, the inventiveapparatus may be constructed to contain or exclude specific features andcomponents according to the intended use of the apparatus, and anyparticular embodiment of the invention, e.g., those depicted in anydrawing herein, may be modified to include or exclude element of otherembodiments. Alternatively, stated, different features of the inventiondescribed above may be combined in different ways. Other aspects,advantages, and modifications within the scope of the invention will beapparent to those skilled in the art to which the invention pertains.

All patents disclosed herein are incorporated by reference in theirentirety to an extent not inconsistent with the above disclosure.

1. An apparatus for transporting fluid to a sample, comprising: asupport structure supporting the sample; a container holding a fluid; aconduit having a fluid-conveying lumen that defines a flow path for thefluid extending from a first terminal opening at the container to asecond terminal opening below the sample; and a means for facilitatingthe sample to absorb the fluid from the second terminal opening, whereinthe flow path does not exhibit an elevated local peak region between thefirst and second terminal openings.
 2. The apparatus of claim 1, whereinthe facilitating means comprises a porous medium.
 3. The apparatus ofclaim 2, wherein the porous medium comprises a glass frit material. 4.The apparatus of claim 1, wherein the facilitating means comprises ameans for positioning an interfacing portion of the sample to absorbfluid through the second terminal opening against gravity.
 5. Theapparatus of claim 4, wherein the positioning means comprises a memberfor controllably pressing the interfacing portion of the sample throughthe second terminal opening.
 6. The apparatus of claim 5, furthercomprising a weight for having a lower surface in contact with thesample, wherein the member includes a spiral grooves that allows forcontrollable positioning of the member relative to the weight and forcontrollably pressing the interfacing portion of the sample through thesecond terminal opening.
 7. The apparatus of claim 1, wherein the secondterminal opening is located at least one millimeter below the supportstructure.
 8. The apparatus of claim 1, wherein the facilitating meansexcludes a pinch valve.
 9. The apparatus of claim 1, further comprisinga means for measuring fluid in the container.
 10. The apparatus of claim9, wherein the means for measuring fluid in the container includes abalance for weighing the fluid in the container.
 11. The apparatus ofclaim 9, wherein the means for measuring fluid in the container iseffective to measure and/or monitor a change in the fluid content in thecontainer over a desired time period.
 12. An apparatus for transportingfluid to a sheet having an upper surface and a lower surface in ahorizontal orientation, comprising: a support structure having an uppersurface and supporting the sheet, wherein the upper surface of thesupport structure contacts no more than 10% of the lower surface of thesheet; a means for immobilizing the sheet on support structure; acontainer holding a fluid; and a conduit having a fluid-conveying lumenthat extends from the container and branches into a plurality ofterminal openings facing the lower surface of the sheet.
 13. A supportstructure for supporting a sample having a lower surface in a horizontalorientation, comprising: a plurality of support members each having anupper surface on which the lower surface of the sample is placed,wherein the upper surfaces are substantially coplanar and define awetting plane; a fixture for immobilizing the support members relativeto each other; and a means for immobilizing a conduit having afluid-conveying lumen relative to the support members such that at leasta portion of the lumen extends upward toward an interface near or withinthe wetting plane to transport fluid along a flow path that terminatesat the lower surface of the sample.
 14. The support structure of claim13, wherein the fixture comprises a plate having an upper surface thesupport members comprises a plurality of fins extending upward from theupper surface of the plate.
 15. The support structure of claim 14,wherein the plate includes a center through-hole about which the finsare radially arranged in a fan out manner, and the flow path extendsthrough the center through-hole.
 16. The support structure of claim 13,supporting the sample, wherein the upper surfaces of the support memberscontacts no more than 10% of the lower surface of the sample.
 17. Anassembly for wetting a sheet, comprising: a sheet having an uppersurface and a lower surface in a horizontal orientation supported by asupport structure having an upper surface, wherein the upper surface ofthe support structure contacts no more than 10% of the lower surface ofthe sheet; and a weight having substantially coplanar lower exterior andinterior surfaces in contact with the upper surface of the sheet. 18.The assembly of claim 17, wherein the lower surfaces are substantiallyconcentric about an axis perpendicular to the plane of the lowersurfaces.
 19. The assembly of claim 17, further comprising a means forpositioning an interfacing portion of the sheet through the support toabsorb liquid upward against gravity.
 20. A method for assessing fluidtransportation anisotropic performance by a sheet having an uppersurface and a lower surface, comprising: (a) obtaining data from a firstabsorption test that employs a single wetting interface at a lowersurface of a first test sheet of the material; (b) obtaining data from asecond absorption test that employs a plurality of wetting interfaces ata lower surface of a second test sheet; and (c) comparing the dataobtained in steps (a) and (b) to determine any differences betweenradial and axial fluid-transporting behavior the sheet of the materialover time.